The memos, stamped “confidential” and kept under wraps for years, portray a White House eager to assert U.S. leadership on climate change. Global warming will have “profound consequences,” one document warns, and the United States “cannot wait” until all scientific questions are resolved before taking action.

The source of the memos: Not the Obama White House, but policy advisers to President George H.W. Bush.

The memos were among several formerly classified documents from the Bush and Reagan administrations obtained under the Freedom of Information Act and released on Wednesday by the National Security Archive. The documents portray senior officials in the two Republican administrations pressing for an aggressive response to international environmental issues of the day — including, during Bush’s term, climate change.

The assertive posture contrasts with the positions taken this week by leading Republican presidential contenders, several of whom publicly mocked Obama’s efforts to secure an international climate treaty in Paris. The GOP-controlled House voted Tuesday to block the administration’s signature regulation to cut greenhouse-gas pollution from U.S. power plants.

The 11 memos released on Wednesday provide snapshots of internal White House deliberations on key environmental issues during the 1980s. Some shed light on the debate over the 1989 Montreal Protocol, which phased out production of industrial chemicals linked to the destruction of the Earth’s ozone layer.

A 1987 memo showed Reagan White House officials pushing back against members of Reagan’s own Cabinet in arguing for a strong treaty safeguarding the thin band of atmospheric ozone that protects the Earth from harmful radiation from space. “Many regard this issue as the most important priority on the global environmental agenda,” John D. Negroponte, then a State Department assistant secretary for the environment, oceans and fisheries, wrote to then-Secretary of State George P. Shultz.

The memo warned against efforts to weaken the treaty, saying such a move “would damage our international credibility, unleash major domestic criticism, and probably result in unilateral U.S.” controls on ozone-depleting chemicals. Negroponte argued instead for a position that is “prudently addressing the environmental risks, while providing a market stimulus and a reasonable time-frame for industry to develop alternate products.”

Two years later, advisers to the George H.W. Bush administration advocated a serious U.S. response to climate change, an issue that was just beginning to draw international attention in the late 1980s. A 1989 memo to then-Secretary of State James A. Baker III asserted that the United States should take a leadership role in the fight against a threat it called “the most far reaching environmental issue of our time.”

“If the climate change within the range of current predictions actually occurs, the consequences for every nation and every aspect of human activity will be profound,” acting assistant secretary Richard J. Smith wrote in the memo.

Smith then cited Baker’s own words to a working-group meeting a few months earlier: “As you yourself stated,” he wrote, “we cannot wait until all the uncertainties have been resolved before we act to limit greenhouse gas emissions and to prepare for whatever climate change we are already committed to.”

The memos reflect the moderate stance on climate change adopted by Republican leaders both in the White House and in Congress throughout the 1980s and 1990s. By contrast, many of today’s GOP successors to Bush and Reagan dispute the scientific consensus on man-made climate change and oppose efforts to reduce greenhouse-gas emissions.

GOP presidential front-runner Donald Trump recently said he is “not a believer” in man-made climate change, an issue he dismissed as something “created by and for the Chinese.”

New Jersey Gov. Chris Christie (R), who in the past has acknowledged the existence of climate change, said Tuesday, “It’s not a crisis.”

“That’s my feeling. I didn’t say I was relying on any scientist,” Christie told MSNBC’s “Morning Joe” program. “I don’t see evidence that it’s a crisis. I don’t.”

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Joby WarrickJoby Warrick joined The Washington Post’s National staff in 1996. He has covered national security, the environment and the Middle East and writes about terrorism. He is the author of two books, including 2015’s “Black Flags: The Rise of ISIS," which was awarded a 2016 Pulitzer Prize for nonfiction. Follow